from land to sea

• Published in: ROM (Toronto) Vol. 50; no. 1
• Main Authors: De Iuliis, Gerry, Haddrath, Oliver
• Format: Magazine Article
• Language: English
• Published: Toronto Royal Ontario Museum 01.04.2017
• Subjects: Aquatic life; Bones; Chromosomes; Deoxyribonucleic acid; DNA; Ears & hearing; Evolution; Fossils; Genomes; Marine mammals; Sound waves; Studies; Swimming; Whales & whaling
• ISSN: 1911-947X

More cow than fish: ROM scientists study how whales evolved to become masters of the seas EVOLUTION Despite superficial similarities to fish, whales are not fish-they are air-breathing mammals whose ancestors lived exclusively on land! Scientists have since verified these observations and now group whales with dolphins and porpoises under the scientific name Cetacea. Some telltale mammalian features of whales are mammary (milk-producing) glands and hair, although these hairs are few, short, and noticeable only around the mouth and face of some species. WHALES' CLOSEST RELATIVES Today, scientists agree that whales belong to a group of hoofed, mainly plant-eating mammals called artiodactyls. FOSSIL WHALES PROVIDE IMPORTANT CLUES Although the whale-artiodactyl relationship is now firmly established, scientists reached agreement on this linkonlyabout30yearsago. Palaeontologists had only bones and teeth to study (soft tissue structures almost never fossilize), and dental evidence suggested that whales were most closely related to certain archaic meat-eating mammals (mesonychids). When scientists found a whale-like ear and an artiodactyl-like ankle in the same fossil skeleton of a terrestrial mammal, they became convinced that whales are artiodactyls-that they came from the same ancestor. BASILOSAURIDS These fossil whales, such as the Dorudon were fully aquatic with flattened, flipper-like forelimbs and relatively immobile wrists Their hind limbs were tiny but projected, fin-like, beyond the body outline.